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Defining, exploring, imaging and assessing reservoirs for potential heat exchange - Potsdam, Germany, Workshop1
Defining, exploring, imaging and assessing reservoirs for potential heat exchange - Potsdam, Germany, Workshop1
6-8 November 2006 GeoForschungsZentrum Potsdam (GFZ)
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Tectonic modelling of non steady-state temperature in the lithosphere
It is a general problem in geothermal exploration to extrapolate temperatures 
measured in shallow depth to greater depth. It is made generally assuming steady-
state condition. Before the extrapolation topographic and paleoclimatic corrections 
of temperatures must be carried out, and the effect of sedimentation, erosion and 
groundwater flow must be taken into account. Additionally, the tectonic processes 
must also be assessed, because they generally result in non steady-state thermal 
field. In this study we present a range of tectonic processes, their thermal models 
and examples how they influence the lithospheric and crustal and sediment 
temperature distribution.
During  extension, the lithosphere is stretched, resulting in a thinned 
lithosphere. In the thermal model pure shear is assumed, which means that each part 
of the lithosphere preserves its original temperature as it rises to shallower 
depth due to thinning. Thus, the geothermal gradient in the lithosphere, and 
consequently the heat flow increases. This mechanism is widely accepted to explain 
the high heat flow in the Western Mediterranean sea, Pannonian basin and Aegean 
region. The thermal model is used to calculate the thermal history of sediments and 
predict maturation of organic materials.
Significant crustal extension may lead to the formation of metamorphic core 
complexes. Metamorphic core complexes are middle or lower crustal rocks uplifted to 
the surface as the overlying rocks are removed by extension. When the extension and 
the uplift is fast the metamorphic core complexes can keep their original 
temperature and geothermal gradient. As they cool or sediments are deposited on top 
of them, the near surface temperature gradient and heat flow can be high, but both 
quantities decrease with depth approaching the original values. Metamorphic core 
complexes are frequently found in the Pannonian basin and the Aegean region and 
their effect on the thermal field can be significant. Furthermore lithospheric 
extension can be accompanied by (often localized) magmatism, generally resulting in 
thermal advection in various levels in the crust.
Opposite to extension shortening and nape stacking reduces the geothermal gradient 
and heat flow. In Europe this mechanism is mainly important in the tectonic and 
thermal history of the Alps.
The tectonic processes are usually accompanied by sedimentation or erosion 
modifying the thermal effects of tectonics. Sometimes a number of  tectonic 
processes are combined or follow each other.
For many examples in Europe it can be shown that heat flow in the crust and mantle 
is not steady state. Consequently, it is not straightforward to extrapolate shallow 
temperatures to greater depth or laterally beyond well control, even if the 
geometry and thermal properties of basins are considered well known. Therefore, to 
obtain reliable thermal models and deep temperature predictions, beyond exsiting 
well control, the tectonic history of the area must be known, correct rock thermal 
properties must be used, and the model results must be calibrated by measured 
temperatures and heat flow data.
Id: 37
Place: GeoForschungsZentrum Potsdam (GFZ)
14473 Potsdam, Telegrafenberg
Starting date:
06-Nov-2006   10:50
Duration: 03'
Contribution type: Poster
Primary Authors: Dr. LENKEY, Laszlo (Department of Geophysics, Eötvös University)
Dr. VAN WEES, Jan-Diederik (TNO, Geo-Energy and Geo-Information)
Co-Authors: Prof. CLOETINGH, Sierd (Faculty of Earth and Life Sciences, Vrije Universiteit)
Prof. HORVATH, Frank (Department of Geophysics, Eötvös University)
Dr. DöVéNYI, Peter (Department of Geophysics, Eötvös University)
Presenters: Dr. LENKEY, Laszlo
Material: slides Slides
poster Poster

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